Application Of PID Automatic Control Technology In Time And Frequency Transsmision Tranceiver

With the development of information society,high precision time and frequency synchronization system plays a more and more important role in production,life and scientific research,such as power grid control,5G communications,global position navigation,square kilometer array and deep space exploration.The early time and frequency synchronization system used satellite links for transmission.The ionosphere and troposphere in the satellite links have great influence on the signal,and the multipath effect of near-ground transmission can degrade the performance of the synchronization system.Compared with satellite links,optical fiber has the advantages of low attenuation and good anti-interference performance,which make it another important transmission method of time and frequency synchronization system.In optical fiber time and frequency transmission,the modulator,as one of the core devices at the transmitting end,has an important influence on the performance of the synchronization system.In the time synchronization system,the rising edge of the 1PPS signal is one of the important indicators to ensure its accuracy.In order to obtain a high extinction ratio,the operating point of the modulator should be stabilized at the null transmission point.In the frequency synchronization system,the signal-noise ratio of the radio frequency signal and its second harmonic suppression ratio are important indicators affecting its transmission performance.Therefore,it is an urgent requirement for the system to accurately and stably control its operating point at the quadrature transmission point.In addition,when performing long distance external field transmission,taking into consideration factors such as volume,weight,and manpower and others,it is particularly important to perfirm remote control and remote monitoring on the core module phase lock loop(PLL)of the frequency synchronization system in the long distance external field transmission,taking into consideration factors such as volume,weight,and manpower and others.This paper mainly studies the control of the operating point of the modulator and the function optimization of the PLL in the optical fiber time and frequency transmission.The control algorithm is the proportion-integration-differential(PID)automatic control algorithm.The main research work includes:1.This paper analyzes the effect of the modulator on the time-frequency transmission performance of the fiber,and draw a conclusion that the operating point of the modulator needs to be controlled accurately and stably.Next,the existing control scheme is investigated and the conclusion is drawn that the control scheme mainly includes pilot method and no pilot method and pilot method introduces pilot signal for transmission point control.In order to avoid the extra interference of pilot signals to the high precision time-frequency synchronous transmission system,the bias control method in the system should be no pilot control method after preliminary analysis of the control scheme.2.Design and experiment of modulator bias control scheme.In time transmission,the optical power detection method based on PID algorithm is used to control the null transmission point,which is tested on the time transfer back-to-back system.The test results are:peak-to-peak value of 106 ps,root mean square value of 13.2 ps,and system stability of 1.23×10-11/s and 9.9×10-13/10000 s.In frequency transmission,the harmonic detection method based on PID algorithm is used to control the quadrature transmission point.Although the method does not include a pilot signal,it can achieve the control effect of the pilot method in the control effect,which is superior to the optical power control method.The test results are:3.0×10-15s and 6.95×10-18/1 0000 s.The control algorithms of both control programs are optimized PID algorithms,that is bidirectional PID algorithms.The difference between the optimized algorithm and the traditional PID control algorithm is that it consists of two precise and unstable PID algorithms,so that the entire control system is stable and accurate.3.The function improvement and experiment of PLL.After analyzing the function of PLL commonly used in frequency synchronization systems,this paper proposes optimization scheme,using the software PLL to realize the function of remote monitoring,among which the core algorithm is PID algorithm.